Exercise Lowers Risk for These 13 Cancer Types

09/08/2016 01:02PM | 6131 views

A large new study confirms that exercise
lowers the risk of many different types of cancer, and it goes a step further:
It shows just how much the reduction in risk is.

People who exercised the most had a 42
percent lower risk of esophageal cancer and a 27 percent lower risk of liver
cancer over 11 years than people who exercised the least, the study of 1.4
million people showed.

Those who exercised the most had:

·
A 26 percent lower risk of lung
cancer

·
A 23 percent lower risk of
kidney cancer

·
A 22 percent lower risk of
stomach cancer

·
A 21 percent lower risk of
endometrial cancer

·
A 20 percent lower risk of
myeloid leukemia

·
A 17 percent lower risk of
myeloma

·
A 16 percent lower risk of
colon cancer

·
A 15 percent lower risk of head
and neck cancer

·
A 13 percent lower risk of
rectal cancer

·
A 13 percent lower risk of
bladder cancer

·
A 10 percent lower risk of
breast cancer

The team at the National Cancer Institute
looked at dozens of cancer studies in the U.S. and Europe, and threw all their
findings together into a single analysis. They compared the people who
exercised more than 90 percent of everyone else in the study to those who
exercised the very least.

The biggest exercisers got in the
equivalent of just over an hour a day of brisk walking, said Steven Moore of
the National Cancer Institute, who led the study.

They included studies that just looked at
strenuous exercise, such as running, and at studies that looked at more
moderate exercise, including swimming and strolling and even vigorous yardwork.

On average, the exercisers did two and a
half hours of moderate exercise, such as walking, every week. This is about the
average for the U.S. as a whole.

"A higher level of leisure-time
physical activity was associated with a 7 percent lower risk of total
cancer," they wrote in their report, published in the Journal of the
American Medical Association's JAMA Internal Medicine.

Exercise has all sorts of benefits, Moore
said. "it can help people reduce their risk of heart disease. It can
reduce the risk of diabetes. It extends life expectancy. And now it appears
that it may reduce the risks of some cancers," Moore told NBC News.

"Furthermore, our results support that
these associations are broadly generalizable to different populations,
including people who are overweight or obese, or those with a history of
smoking."

Obesity is a well-known risk factor for
cancer, but exercise protected even obese people from cancer, the study found.
On average, the people in the study were slightly overweight.

"This finding may help encourage those
who are overweight or obese to be physically active," Moore's team wrote.

While it's always possible that people who
are able to exercise more are healthier in other ways and less likely to
develop cancer for some other reason, cancer experts say the evidence is very
convincing that exercise directly affects the growth of tumors.

There are three possible ways exercise
might lower cancer risk, Moore said. It can lower levels of hormones such as
estrogen, which in turn lowers breast and endometrial cancer risk, he said. It
helps the body better regulate insulin, and it may lower inflammation.

One odd finding: exercise lowered the risk
for lung cancer, but only among current and former smokers.

Exercisers did have a higher risk of
melanoma, probably because they often exercised outside. The researchers stress
that if you exercise outdoors, you need to use sunscreen.

And men who exercised had a higher rate of
prostate cancer. "There is no known biologic rationale to explain this
association," the researchers wrote.

It's possible, they said, that men who are
physically active also are more likely to go to the doctor and get screening
tests for prostate cancer, which in turn show up prostate tumors that are
slow-growing and not necessarily dangerous to the man.

Doctors should be prescribing exercise to
their patients, Moore's team said. Only about half of Americans get the minimum
recommended amount of exercise.